1. Field of the Invention
This invention relates generally to the field of Magnetic Resonance Imaging (MRI) systems for generating diagnostic images of a patient""s internal organs and more particularly, this invention relates to improved MRI systems exhibiting decreased interference between the magnetic field used for producing diagnostic images and spurious magnetic fields created by ancillary equipment, such as the electric motors used for driving the pistons of the contrast media injectors. Additionally, the system employs an improved communication link between an externally located system controller and the injection head control unit which is located within the electromagnetic isolation barrier of the magnetic imaging suite.
2. Description of the Related Art
It has become recognized that MRI systems require isolation from external sources of electromagnetic fields, if optimum image quality is to be obtained from MRI diagnostic procedures. Conventional MRI systems have typically employed some form of electromagnetic isolation chamber which is generally a room enclosed by copper sheeting or conductive mesh material that isolates the room from undesirable sources of electromagnetic radiation and the electromagnetic noise inherent in the atmosphere.
In order to realize the full benefit of the shielded room, these systems employ a controller for the contrast media injector portion of the system which is isolated from the media injector. Such isolation is effected to prevent undesirable electromagnetic radiation generated by the system controller from interfering with the signals used to create the magnetic resonance images.
The external, isolated location of the system controller creates various problems associated with the installation and operation of these systems. One such problem is the need to provide a communications link between the externally located controller and the contrast media injectors, without introducing extraneous electromagnetic radiation. That is, there is a need to provide electrical power supply lines for operation of the contrast media injectors and the injector control circuitry while maintaining the integrity of the electromagnetic shield.
Previous attempts to solve these problems included drilling holes in the wall of the electromagnetic shield for inserting the necessary lines or, alternatively, laying the lines under a shielded floor of the imaging room. These alternatives have proven to be less than optimum, since spurious radiation arose from the presence of the various supply cables within the shielded imaging suite. Additionally, MRI systems which employed these solutions required substantially site dedication and were therefore not very portable.
Another problem associated with conventional magnetic resonance imaging systems is the interference which occurs between the high power magnetic field used for generating the magnetic resonance image and the magnetic fields created by the electric motors which control the operation of the contrast media injection heads. The magnetic field generated by the magnet of the magnetic resonance imaging system is extremely powerful and adversely affects the operation of the electric motors used in the injector head. Additionally, operation of the electric motors in close proximity to the magnetic field used to generate the magnetic resonance image also has an adverse impact on the quality of the resulting image.
In conventional MRI systems, the injection head unit is located adjacent to the patient being examined and the electric motors associated with the injection syringes are directly connected to the syringe pistons. Characteristically, the syringes and the drive motors have been mounted on the injection head unit. The close proximity of the electric motors to the magnetic field used for generating the magnetic resonance image typically resulted in a decrease in motor performance and the ability to control the electric motors used in the injector heads, as well as an overall decrease in system performance.
Accordingly, it is an object of the present invention to provide an improved magnetic resonance imaging contrast media delivery system having decreased interference between the magnetic field used to obtain the magnetic resonance image and the magnetic fields created by ancillary equipment.
It is a further object of this invention to provide an MRI system which minimizes the interference between fields created by the electric motors used to drive the contrast media injection plungers and the magnetic field used to generate the magnetic resonance image.
It is another object of the present invention to provide an MRI contrast media injection system having an improved communication link between the system controller and the injection control unit.
Numerous other objects and advantages of the present invention will be apparent from the following summary, drawings and detailed description of the invention and its preferred embodiment; in which: